Transmission link assemblies

ABSTRACT

An assembly comprises at least first and second transmission links. Each transmission link controls movement of a respective element coupled to a first side of the transmission link, under control of a common drive source coupled to a second side of the transmission link. A synchronizing unit is interposed between the first side and the second side of each transmission link, to synchronize movement of the respective elements by the common drive source.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 15/546,335, having anational entry date of Jul. 26, 2017, which is a national stageapplication under 35 U.S.C. § 371 of PCT/EP2015/058934, filed Apr. 24,2015, which are both hereby incorporated by reference in their entirety.

BACKGROUND

In some printers, a common drive source, for example a motor andassociated drive gear, can be used to control movement of elements suchas printheads, or a printbar comprising printheads. In such examples,multiple transmission links can be provided for controlling movement ofthe various elements, or for controlling movement of the printbar,whereby the multiple transmission links are controlled by the commondrive source.

BRIEF DESCRIPTION OF DRAWINGS

Examples will now be described, by way of non-limiting example, withreference to the accompanying drawings, in which:

FIG. 1 is an example of an assembly according to the disclosure;

FIG. 2 is an example of a synchronizing unit for use with an assemblyaccording to examples described herein;

FIG. 3 is an example of another assembly according to the disclosure;

FIG. 4a is an example of another assembly according to the disclosure;

FIGS. 4b and 4c show further details of the example of FIG. 4 a;

FIG. 5 shows an example of a method according to the disclosure; and

FIG. 6 shows a method according to another example.

DESCRIPTION

FIG. 1 shows an assembly according to a first example. The assemblycomprises at least first and second transmission links 10, eachtransmission link 10 controlling movement of a respective element 14coupled to a first side 10 _(A) of the transmission link 10, undercontrol of a common drive source 16 coupled to a second side 10 _(B) ofthe transmission link 10. A synchronizing unit 12 is interposed betweenthe first side 10 _(A) and the second side 10 _(B) of each transmissionlink 10, to synchronize movement of the respective elements 14 by thecommon drive source 16.

In the example shown, there are provided three transmission links 10,labelled 10 ₁, 10 ₂ and 10 _(N) respectively. The first and second sidesof transmission link 10 ₁, for example, are labelled 10 _(1A) and 10_(1B) respectively. It is noted that any plurality of transmission links10 and corresponding elements 14 may be provided. The elements 14 maycomprise separate or individual elements whose movement is to becontrolled, as shown in FIG. 1. In another example (which will bedescribed later in FIG. 3) the elements 14 form part of a commonelement, for example portions or locations on a printbar 14.

In one example, the synchronizing unit 12 is switchable between a lockedmode of operation and an unlocked mode of operation. In the locked modeof operation the synchronizing unit 12 causes a respective element 14 tomove in direct relationship to movement of the transmission link 10 intowhich the synchronizing unit 12 is interposed. In the unlocked mode ofoperation the synchronizing unit 12 allows movement of the first side 10_(A) of the transmission link 10 relative to the second side 10 _(B) ofthe transmission link 10, the relative movement being independent of thecommon drive source 16. This relative movement in the unlocked mode ofoperation can compensate, for example, for any differences in functionaldistance between the common drive source 16 and the respective elements14.

The differences in functional distance, or functional length, may becaused for example by dimensional factors such as tolerances ofcomponent parts that constitute the transmission system, mechanism playsbetween component parts, backlash in the transmission system,deflections in various components parts, or other factors.

In the example of FIG. 1, the at least first and second transmissionlinks 10 comprise elongated shafts to control linear movement along anaxis corresponding to the axis of the elongated shafts. In such anexample a synchronizing unit 12 may comprise a device body 13 comprisinga female portion 13 _(A) coupled to one side of the elongated shaft (forexample the first side 10 _(A)), and a male portion 13 _(B) coupled tothe other side of the elongated shaft (for example the second side 10_(B)). For example, for the first transmission link 10 ₁ of FIG. 1, thesynchronizing unit 12 ₁ comprises a device body 13 ₁ comprising a femaleportion 13 _(1A) coupled to a first side 10 _(1A) of the elongatedshaft, and a male portion 13 _(1B) coupled to a second side 10 _(1B) ofthe elongated shaft. The same applies to the other transmission links 10₂ and 10 _(N) of FIG. 1.

In the example of FIG. 1, a synchronizing unit 12 further comprises abiasing element 15 to bias the female and male portions 13 _(A), 13 _(B)apart. The synchronizing unit 12 further comprises a locking member 17to allow movement of the female portion 13 _(A) relative to the femaleportion 13 _(B) when the locking member 17 is in an unlocked position,and prevent movement of the female portion 13 _(A) relative to thefemale portion 13 _(B) when the locking member 17 is in a lockedposition. For example, for the first transmission link 10 ₁ of FIG. 1,the synchronizing unit 12 ₁ comprises a biasing element 151 to bias thefemale and male portions 13 _(1A), 13 _(1B) apart. The synchronizingunit 12 ₁ further comprises a locking member 17 ₁ to allow movement ofthe female portion 13 _(1A) relative to the male portion 13 _(1B) whenthe locking member 17 ₁ is in an unlocked position, and prevent movementof the female portion 13 _(1A) relative to the male portion 13 _(1B)when the locking member 17 ₁ is in a locked position. The same appliesto the other transmission links 10 ₂ and 10 _(N) of FIG. 1.

In one example the female portion 13 _(A) is fixedly coupled to thefirst side 10 _(A) of the transmission link 10, and the male portion 13_(B) fixedly coupled to the second side 10 _(B) of the transmissionlink, or vice versa. For example, for the first transmission link 10 ₁of FIG. 1 the female portion 10 _(1A) is fixedly coupled to the firstside 10 _(1A) of the transmission link 10, and the male portion 13 _(1B)fixedly coupled to the second side 10 _(1B) of the transmission link. Itis noted that references to female and male portions 13 _(A), 13 _(B)are intended to embrace any structure of parts that cooperate to allowmovement relative to one another when the locking member 17 is in theunlocked position, and do not necessarily need one portion to fit withinthe other during such movement.

The example of FIG. 1 allows movement of the elements 14, via control ofthe common drive source 16 and the transmission links 10, to besynchronized by the manner in which each synchronizing unit caneffectively alter its length to compensate for structural differences ortolerances in the transmission system, such that the elements can beactuated in a coordinated manner.

During a calibration mode of operation, for example, the locking members17 of each of the synchronizing units can be moved to an unlockedposition. When the locking members 17 are in the unlocked position, thebiasing elements 15 cause the male and female portions of eachsynchronizing unit 12 to be biased apart. As such, the functional lengthof each transmission link is increased (or decreased in somecircumstances) to compensate for different functional distances betweeneach respective element 14 and the common drive source 16. After asettling period during the unlocked stage of the calibration mode, e.g.after the synchronizing units have adjusted to the different functionaldistances, the synchronizing units can be locked, and the calibrationmode exited. In one example the synchronizing units can all be moved tothe unlocked position together or in parallel, adjusted to match therequired functional length, and then locked together or in parallel. Inanother example, each synchronizing unit can be unlocked, adjusted andlocked individually, before moving on to the next synchronizing unit.

In the example of FIG. 1, it can be seen that the height of the secondelement 14 ₂ (which as shown in this example is greater than the heightof the first element 14 ₁, thus having a smaller effective functionaldistance between the element 14 ₂ and the common drive source 16) hasacted against the force of the biasing element 15 ₂ which is trying tobias the female portion 13 _(2A) and male portion 13 _(2B) of thesynchronizing unit 12 ₂ apart, resulting in the functional length of thesecond transmission link 10 ₂ being decreased compared to that of thefirst transmission link 10 ₁. Also in this example, it can be seen thatthe height of the third element 14 _(N) (which as shown in this exampleis less than the height of the first element 14 ₁, thus having a largereffective functional distance between the element 14 _(N) and the commondrive source 16) has resulted in the biasing element 15 _(N) biasing thefemale portion 13 _(NA) and the male portion 13 _(NB) of thesynchronizing unit 12 _(N) apart, resulting in the functional length ofthe third transmission link 10 _(N) being increased compared to that ofthe first transmission link 10 ₁. In this way, according to someexamples the synchronizing units 12 act to change or alter thefunctional lengths of the transmission links which control differentelements from a common drive source.

It is noted that although the example of FIG. 1 shows biasing elements15 located between the male and female portions of the synchronizingunits for biasing them apart, other biasing element arrangements mayalso be provided for biasing the male and female portions apart, forexample biasing elements arranged to pull the male and female portionsapart (or to rotate male and female portions in a rotationalsynchronizing device described later). In some examples the biasingelements are strong enough to push or pull the male and female portionsone against the other, preloading the whole transmission link byallowing relative movement between the male and female portions. In someexamples the biasing elements are arranged to provide a controlledforce, for example a similar or same force to the amount that thetransmission link will withstand under normal operating conditions. Insome example the biasing force may be modified (increased or decreased),for example if the transmission link inertia can affect the positionalaccuracy of the device due to inertial deflections. It is noted that anyform of biasing elements may be used, including for example wire springs(e.g. traction, compression, torsion), or gas cylinders or springs, orhydraulic cylinders, magnets, electric motors (linear or rotational), orother biasing elements that can provide force while allowing relativemovement.

It is also noted that although the example of FIG. 1 is shown ascompensating for differences in the dimensions of the elements 14, thesynchronizing units 12 may also compensate for dimensional differencesor tolerances elsewhere in the transmission system, includingdeflections or deformations when transmission links are working undernormal working loads or conditions.

In the examples described herein, the synchronizing units effectivelyprovide an adjustable portion within a transmission link, which allowsthe length of the transmission link to be adjusted to match thefunctional length needed for a particular transmission link within theoverall transmission system.

Thus, the example of FIG. 1 can act to compensate for differentdistances between the elements 14 and the common drive source 16, forexample caused by different heights of elements 14, different lengths oftransmission links 10, or other tolerances in the transmission system.For example, if the different transmission links have very differentlengths through different rigidities or tolerances, examples describedherein can absorb the positional error sources, including those thatstem from rigidity issues.

In some examples, the female and male portions 13A, 13B may also beprovided with different degrees of movement relative to one another whenthe locking member 17 is in the unlocked position. For example, aplurality of bias settings may be provided when the synchronizing unit12 is operating in the unlocked mode of operation. The plurality of biassettings may be chosen in one example to cater for the different forcesexperienced in a particular application.

FIG. 2 shows further details of a synchronizing unit 12 according to oneexample. As with FIG. 1, the synchronizing unit 12 comprises a devicebody 13 comprising a first portion 13 _(A) (for example a femaleportion) coupled to a first side 10A of the transmission link, and asecond portion 13B (for example a male portion) coupled to a second side10 _(B) of the transmission link 10. The synchronizing unit 12 comprisesa biasing element 15 to bias the first and second portions 13 _(A), 13_(B) apart. The synchronizing unit 12 further comprises a locking member17 to allow movement of the first portion 13 _(A) relative to the secondportion 13 _(B) when the locking member 17 is in an unlocked position,and prevent movement of the first portion 13 _(A) relative to the secondportion 13 _(B) when the locking member 17 is in a locked position. Inone example a locking member 17 allows free movement between male andfemale portions in the degree of freedom that is being preloaded bymeans of the biasing element, without interfering in the transmissionlink length which is being adjusted. In one example the design of alocking member takes account of the degree of freedom that needs to belocked. In some examples, a locking member acts to clamp the male andfemale portions when in the locked position, at any position along theirrelative movement path.

The locking members may be controlled manually, or automatically using acontrol mechanism, or both.

From the above it can be seen that, for a multilink transmission systemwhich moves different elements in a coordinated manner with one sourceof power, by means of the examples described herein an accurate andcoordinated or synchronized movement can be obtained.

FIG. 3 shows an assembly according to another example, in which a commonelement 14, for example a printbar, is actuated from first and secondends using a common drive source 16, such as a common motor andassociated drive gear. A printbar is a beam where the printheads aresupported. The printbar beam is a mobile part that allows printheads toreach different positions for printing and servicing purposes.

The assembly of the example of FIG. 3 comprises at least first andsecond transmission links 10, each transmission link 10 controllingmovement of a respective element 14 coupled to a first side 10 _(A) ofthe transmission link 10, under control of a common drive source 16coupled to a second side 10 _(B) of the transmission link 10. In thisexample the respective elements, whose movement is being controlled,comprise elements that form part of a common element, for exampleportions or locations on a printbar. A synchronizing unit 12 isinterposed between the first side 10 _(A) and the second side 10B ofeach transmission link 10, to synchronize movement of the respectiveelements 14, for example the orientation of a printbar relative to aprintzone 30, using the common drive source 16.

As with the example of FIG. 1, the synchronizing units 12 of FIG. 3 canbe operated in a locked and an unlocked mode, with the synchronizingunits set to compensate for any differences in functional distance orlength when in the unlocked mode, which is then applied when operatingin the locked mode. It is noted that additional transmission links maybe provided.

The example of FIG. 3 therefore provides an accurate and coordinated wayto move the first and second printbar ends. This enables the printbar tobe controlled such that it remains parallel to a printzone 30, such thatprintheads coupled to the printbar also remain parallel to the printzone30. As mentioned above in FIG. 1, in some examples the synchronizingunits may be adjusted together, while in other examples they areadjusted individually. In one example the adjustment may be carried outby braking (or locking) the common drive source (e.g. braking andlocking the motor), placing the synchronizing units in an unlocked mode,adjusting the transmission links (for example such that the printbar isat a desired orientation, such as parallel to the printzone), placingthe synchronizing units in the locked mode, and releasing the commondrive source (motor).

In the examples of FIGS. 1 to 3 the synchronizing units are applied in atransmission system involving linear movement. In other examples, suchas that illustrated in FIG. 4a , the synchronizing units can be appliedin a transmission system involving rotational movement.

In FIG. 4a , there is shown a transmission link 10 for controllingmovement of a respective element (not shown) coupled to a first side 10_(A) of the transmission link 10, under control of a common drive source(not shown) coupled to a second side 10 _(B) of the transmission link10, or vice versa. Other such transmission links may also be driven bythe common drive source, each transmission link controlling movement ofan associated element. A synchronizing unit (comprising a device body13, biasing element 15 and locking member 17) is interposed between thefirst side 10 _(A) and the second side 10 _(B) of the transmission link10, to synchronize movement of an element driven by a common drivesource, with other elements driven by the common drive source viatransmission links 10 similar to that of FIG. 4 a.

Thus, the transmission link in the example of FIG. 4a comprises arotatable transmission link to control rotational movement about anaxis, and wherein the synchronizing unit comprises a device bodycomprising a first portion coupled to one side of the rotatabletransmission link, and a second portion coupled to the other side of therotatable transmission link. The biasing element biases the first andsecond portions apart in a rotational direction. The locking memberallows movement of the first portion relative to the second portion whenthe locking member is in an unlocked position, and prevents movement ofthe first portion relative to the second portion when the locking memberis in a locked position.

FIGS. 4b and 4c shows further details of a locking member 17 accordingto the example of FIG. 4, of the type comprising a fastener, such as ascrew 17 _(A), which cooperates with a slot 17 _(B). FIG. 4b shows thetransmission link 10 adjusted such that the screw 17 _(A) lies towardsone end of the slot 17 _(B) (for example when the male and femaleportions of the transmission link 10 are at the end of one range oftheir relative movement), while FIG. 4c shows the transmission link 10adjusted such that the screw 17 _(A) lies towards the other end of theslot 17 _(B) (for example when the male and female portions of thetransmission link 10 are at the other end of their range of relativemovement). In this example the screw can be unscrewed to place thelocking member in an unlocked mode, to allow movement of the male andfemale portions of the transmission link 10, and the screw thentightened when the screw is at the appropriate point along the slot,i.e. when the functional distance is adjusted to the appropriate pointby the biasing element(s), to place the locking member in the lockedmode. It is noted that other locking member arrangements can also beused in other examples.

Thus, as with the examples of FIGS. 1 to 3, the synchronizing unit canbe operated in an unlocked mode of operation to allow the synchronizingunit to compensate for any differences in functional distance, e.g.rotational distance in this example, in the transmission system. Thedifferences in functional distance, or functional length, may be causedfor example by dimensional factors such as tolerances of component partsthat constitute the transmission system, mechanism plays betweencomponent parts, backlash in the transmission system, deflections invarious components parts, or other factors.

FIG. 5 shows a method according to another example, to compensate fordifferent functional distances in a transmission system in whichmovement of at least first and second elements is controlled by a commondrive source 16 via at least first and second transmission links. Themethod comprises interposing a synchronizing unit 12 in each of the atleast first and second transmission links, as shown in 501. During acalibration mode of operation 503, the synchronizing units 12 areadjusted to compensate for variations in functional distance between thecommon drive source 16 and the respective elements being controlled.

Referring to FIG. 6, in one example, the method comprises placingsynchronizing units into an unlocked mode of operation, in which eachsynchronizing unit can preload a transmission link where it isinterposed, to allow adjustment of the functional distance of thetransmission link, 601, adjusting the functional distances of thetransmission links, 603, and locking the synchronizing units to fix thefunctional distances previously adjusted, 605.

In the methods of FIG. 5 or 6, a transmission link may comprise a lineartransmission link or a rotatable transmission link.

In some examples the transmission is set and retained in a functionalposition, and the lock/unlock members released, such that all forcegenerators or biasing elements will place the transmission links underfunctional stresses, simulating deformations and absorbing all existingplays and backlashes. Then, the lock/unlock members can be locked,holding each transmission link in the functional lengths and positionthat enable them to work in a coordinated manner under functionalconditions.

In another example, a method comprises placing the synchronizing unitsinto an unlocked mode of operation, in which each synchronizing unitexpands or contacts to a functional distance of its correspondingtransmission, allowing the synchronizing units to settle to thefunctional distances of their respective transmission links, and lockingthe synchronizing units to fix the functional distances.

By means of some examples described above, when a multilink transmissionsystem, for example in a printer, has to move different elements in acoordinated manner using a common source of power, the examples enablepositional error sources to be absorbed, such positional error sourcescomprising for example functional deformations, variability indimensional tolerances, or differential rigidities in differentcomponents. Therefore, according to at least some examples, an accurateand coordinated movement can be provided

Thus, when a mechanism comprises a common mechanical power source thatmoves more than one element (or different parts of the same element),the examples enable such element(s) to be actuated in a more precisecoordinated fashion, such that dimensional issues such as tolerances,mechanisms plays, backlash, deflections, etc, can be compensated for.

The examples described herein allow the synchronizing of the movement oftransmissions that transfer power or movement to a number of elementsthat are to be actuated in a coordinated manner. For example, theexamples described herein may be used to control movement of a printbarlift mechanism.

The examples described herein can be used with both linear androtational movements, for example by interposing an appropriatesynchronizing unit in a respective transmission link. The synchronizingunits may also be used in combination with both linear and rotationalmovement control.

In some examples, a transmission link comprises a fixed functionallength when the assembly is operating in a locked mode of operation, andwherein the functional length of the transmission link can be changedwhen the assembly is operating in an unlocked mode of operation.

In some examples, the synchronizing units are structured such that thedegree of possible relative movement between first and second portionsof a device body of a synchronizing unit is selected to be greater thana possible dimensional tolerance to be compensated for.

In one example, a printer apparatus comprises an assembly orsynchronizing unit as described in any of the examples described herein.

The word “comprising” does not exclude the presence of elements otherthan those listed in a claim, “a” or “an” does not exclude a plurality,and a single processor or other unit may fulfil the functions of severalunits recited in the claims.

The features of any dependent claim may be combined with the features ofany of the independent claims or other dependent claims.

1. A synchronizing unit comprising: a device body comprising a firstmember coupled, during use, to a first side of a transmission link, anda second member coupled, during use, to a second side of thetransmission link, wherein the device body has an axis that is parallelto an axis of the transmission link; a biasing element to bias the firstand second members apart; and a locking member to allow movement of thefirst member relative to the second member along the axis of the devicebody when the locking member is in an unlocked position, and preventmovement of the first member relative to the second member along theaxis of the device body when the locking member is in a locked position.2. The synchronizing unit of claim 1, wherein the biasing elementcomprises a spring.
 3. The synchronizing unit of claim 1, wherein thebiasing element comprises a gas cylinder.
 4. The synchronizing unit ofclaim 1, wherein the biasing element comprises a hydraulic cylinder. 5.The synchronizing unit of claim 1, wherein the biasing element comprisesa magnets.
 6. The synchronizing unit of claim 1, wherein the firstmember is to fixedly couple to the first side of the transmission link,and the second member is to fixedly couple to the second side of thetransmission link.
 7. A printer apparatus comprising a synchronizingunit as claimed in claim
 11. 8. A method for a transmission system inwhich movement of a plurality of elements is controlled by a commondrive source via a plurality of transmission links, the methodcomprising: interposing a plurality of synchronizing units in theplurality of transmission links, each respective transmission link ofthe plurality of transmission links extending along a respective axisbetween the common drive source and a respective element of theplurality of elements, the respective element to engage a first side ofthe respective transmission link, and the common drive source to engagea second side of each of the plurality of transmission links; and duringa calibration mode of operation of the transmission system, adjustingthe plurality of synchronizing units to compensate for variation indistances between the common drive source and the plurality of elementsbeing controlled, to synchronize movement of the plurality of elementsby the common drive source.
 9. The method of claim 8, wherein eachrespective synchronizing unit of the plurality of synchronizing units isinterposed between the first side and the second side of the respectivetransmission link, each respective synchronizing unit comprising a firstmember moveable relative to a second member when the first and secondmembers are unlocked from one another, and the first member and thesecond member being moveable relative to one another to compensate forthe variation in the distances between the common drive source and theplurality of elements.
 10. The method of claim 9, further comprising:moving the first member and the second member of a first synchronizingunit of the plurality of synchronizing units relative to one anotherwhen unlocked by a first amount to set a target distance between thecommon drive source and a first element of the plurality of elements;and moving the first member and the second member of a secondsynchronizing unit of the plurality of synchronizing units relative toone another when unlocked by a second amount to set the target distancebetween the common drive source and a second element of the plurality ofelements, the first amount different from the second amount.
 11. Themethod of claim 10, further comprising: locking the first member and thesecond member of the first synchronizing unit relative to one anotherafter the moving by the first amount; and locking the first member andthe second member of the second synchronizing unit relative to oneanother after the moving by the second amount.
 12. The method of claim9, wherein each respective synchronizing unit of the plurality ofsynchronizing units is switchable between a locked mode of operation andan unlocked mode of operation, the method comprising: in the locked modeof operation, moving, by the respective synchronizing unit therespective element in direct relation to movement of the respectivetransmission link into which the respective synchronizing unit isinterposed; and in the unlocked mode of operation, unlocking the firstand second members of the respective synchronizing unit from oneanother, and the respective synchronizing unit allows movement of thefirst side of the respective transmission link relative to the secondside of the respective transmission link, the movement being independentof the common drive source, to compensate for the variation in thedistances between the common drive source and the plurality of elements.13. The method of claim 9, wherein a first transmission link of theplurality of transmission links comprises an elongated shaft to controllinear movement along the respective axis of the first transmissionlink, and wherein a first synchronizing unit interposed in the firsttransmission link comprises: a device body comprising the first membercoupled to one side of the elongated shaft, and the second membercoupled to another of the elongated shaft; a biasing element to bias thefirst and second members apart; and a locking member to allow movementof the first member relative to the second member when the lockingmember is in an unlocked position, and prevent movement of the firstmember relative to the second member when the locking member is in alocked position.
 14. The method of claim 9, wherein a first transmissionlink of the plurality of transmission links comprises a rotatabletransmission link to control rotational movement about an axis, andwherein a first synchronizing unit interposed in the first transmissionlink comprises: a device body comprising the first member coupled to oneside of the rotatable transmission link, and the second member coupledto the other side of the rotatable transmission link; a biasing elementto bias the first and second members apart in a rotational direction;and a locking member to allow movement of the first member relative tothe second member when the locking member is in an unlocked position,and prevent movement of the first member relative to the second memberwhen the locking member is in a locked position.
 15. The method of claim8, wherein each element of the plurality of elements is a separateelement whose movement is controlled by a respective transmission linkof the plurality of transmission links.
 16. The method of claim 8,further comprising, during the calibration mode of operation: placingthe plurality of synchronizing units into an unlocked mode of operation,in which each respective synchronizing unit can preload the respectivetransmission link where the respective synchronizing unit is interposed,to allow adjustment of a distance of the respective transmission link;after placing the plurality of synchronizing units into the unlockedmode of operation, adjusting distances of the plurality of transmissionlinks; and locking the plurality of synchronizing units to fix thedistances of the plurality of transmission links adjusted by theadjusting.
 17. The method of claim 8, wherein the plurality oftransmission links comprise linear transmission links.
 18. The method ofclaim 8, wherein the plurality of transmission links comprise rotatabletransmission links.
 19. The method of claim 8, wherein the common drivesource is positioned on a first side of the plurality of elements, andthe respective axes along which the plurality of transmission linksextend are parallel to one another.